Every year, approximately 50 out of 1,000 babies are born with a congenital heart defect (CHD) in the United States. Our long range goal is to understand the signaling mechanisms involved in heart septation and valve formation as miscues during these events constitute the most common cause of CHD. The heart valves and septae arise from molecular interactions between cardiac cushion cells and extracellular matrix components such as hyaluronan (HA). Throughout development, HA is primarily synthesized by the transmembrane protein hyaluronan synthase-2 (Has2). Thus, the objective of this application is to determine the role of key signaling proteins in Has2 activation and HA mediated cell invasion. HA can activate signaling effectors such as ERK and NFkB which, at the same time, have been shown to induce important regulators of cell behavior such as the Snail proteins. However, to this point no functional connection has been established between HA, NFkB and Snail proteins and the promotion of cellular invasion, a crutial process during cardiac development. Hence, our central hypothesis is that the activation of Has2 and subsequent production of HA leads to cell invasion via the induction of NFkB and Snail family members. We propose the following two specific aims to test our hypothesis: 1. Define the molecular modifications and interactions that regulate Has2 activity. 2. Determine whether HA signals through NFkB and Snail to induce invasive cellular migration. For our studies, we will utilize mouse embryonic fibroblast cells to perform a variety of experiments such as NFkB activity assays, real-time PCR, Western blots, immunoprecipitations, cloning, siRNA techniques, invasion and proliferation assays, etc. Our research will define the convergence of important signaling pathways for heart development through the actions of Has2 and its product hyaluronan. Understanding how these molecules exert their actions is crucial to help uncover the underlying causes for congenital heart defects. With this knowledge we expect to facilitate the development of diagnostic tools and more effective treatment for these cardiac diseases.